Communication device and communication method

ABSTRACT

One embodiment provides a communication device for transmitting a video to an external device through first to third transmission lines, the communication device including: a transmission module configured to transmit first color difference information and second color difference information concerned with adjacent two pixels through the first transmission line, to transmit first luminance information concerned with one of the two pixels through the second transmission line, and to transmit second luminance information concerned with the other of the two pixels through the third transmission line.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority/priorities from Japanese PatentApplication No. 2011-231186 filed on Oct. 20, 2011; and Japanese PatentApplication No. 2012-111976 filed on May 15, 2012; the entire contentsof which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a communication deviceand a communication method.

BACKGROUND

There is known HDMI (High Definition Multimedia Interface)Specification, as a multimedia interface between a video transmittersuch as a DVD player or a set-top box and a video receiver such as a TVset or a monitor. A device having an HDMI output terminal is calledsource device, whereas a device having an HDMI input terminal is calledsink device. For example, the video transmitter is a source device,whereas the video receiver is a sink device. And, a device having bothan HDMI input terminal and an HDMI output terminal to function as bothof a source device and a sink device is called repeater device.

An HDMI communication device for performing communication according tothe HDMI Specification has: a TMDS (Transition Minimized DifferentialSignaling) transmission module which transmits video, audio andauxiliary information; a +5V power supply signal transmission module forinforming a sink device or a repeater device of connection in the formof a source ready signal when a source device is connected to the sinkdevice or the repeater device; an HPD (Hot Plug Detect) signaltransmission module which transmits an HPD signal as a sink ready signalindicating that the sink device or the repeater device is ready forreceiving video information; an EDID (Extended Display IdentificationData) transmission module which transmits EDID which are data such asproduct information of the connected sink device and an adequate videoformat; an HDCP (High-bandwidth Digital Content Protection)authentication module which authenticates the sink device; and a CEC(Consumer Electronics Control) transmission module which transmits CECincluding a device control signal and a control protocol.

There is a recently increasing demand for high-definition video of3840×2160 called 4K2K. However, in transmission of such high qualityvideo, the load imposed on a communication interface will increase.

BRIEF DESCRIPTION OF DRAWINGS

A general architecture that implements the various features of thepresent invention will now be described with reference to the drawings.The drawings and the associated descriptions are provided to illustrateembodiments and not to limit the scope of the present invention.

FIG. 1 illustrates a use form of a communication device according to anembodiment.

FIGS. 2 and 3 illustrate a system configuration of the communicationdevice.

FIGS. 4A to 4C illustrate examples of a pixel encoding format of videotransmitted by the communication device.

FIGS. 5A to 5C illustrate examples of a video timing format used by thecommunication device.

FIG. 6 illustrates a structure of data stored by the communicationdevice.

FIG. 7 illustrates a structure of data transmitted by the communicationdevice.

FIG. 8 illustrates a video transmission flow in the communicationdevice.

FIG. 9 illustrates a video reception flow in the communication device.

DETAILED DESCRIPTION

In general, one embodiment provides a communication device fortransmitting a video to an external device through first to thirdtransmission lines, the communication device including: a transmissionmodule configured to transmit first color difference information andsecond color difference information concerned with adjacent two pixelsthrough the first transmission line, to transmit first luminanceinformation concerned with one of the two pixels through the secondtransmission line, and to transmit second luminance informationconcerned with the other of the two pixels through the thirdtransmission line.

An embodiment will be described blow with reference to the drawings.

FIG. 1 illustrates a data transmission system according to a firstembodiment.

In this data transmission system, a playback device 100 serving as asource device and a display device 200 serving as a sink device in thisembodiment are connected to each other by an HDMI cable 300.

The playback device 100 has a reading module 101 and a storage module102 (not shown in FIG. 1). The playback device 100 has a function ofplaying back (decoding) coded video data stored in an optical disk orthe storage module 102. The playback device 100 then outputs decodedvideo data to the display device 200 through the HDMI cable 300. Thedisplay device 200 has a display module 203 and displays video based onreceived video data.

FIG. 2 illustrates the system configuration of the playback device 100and the display device 200.

The playback device 100 has the reading module 101, the storage module102, a decoding module 103, an HDMI transmission module 104, etc. Thereading module 101 reads coded video data stored in an optical disk andoutputs the coded video data to the decoding module 103. For example,the storage module 102 stores coded video data which has been recorded,and outputs the stored coded video data to the decoding module 103. Thedecoding module 103 decodes the input coded video data, for example,into video data of 8 bits in each of RGB, (YCrCb) 4:2:0 format, (YCrCb)4:2:2 format or (YCrCb) 4:4:4 format. The HDMI transmission module 104converts the decoded video data into a video signal of a specifictransmission format, and outputs the video signal to the display device200 through the HDMI cable 300.

The display device 200 has an HDMI reception module 201, a displayprocessor 202, the display module 203, a tuner 204, a signal processor205, etc. The HDMI reception module 201 receives a video signal andconverts the received video signal into video data of a format (e.g.baseband data of 8 bits in each of RGB) compatible with the displayprocessor 202. The display processor 202 converts the video datainputted from the HDMI reception module 201 and the signal processor 205into a video signal of a format compatible with the display module 203,and outputs the video signal to the display module 203. The displaymodule 203 displays video based on the input video signal.

The tuner 204 receives a television broadcasting signal. The signalprocessor 205 converts the received broadcasting signal into video data,and outputs the video data to the display processor 202.

FIG. 3 illustrates the system configuration of the HDMI transmissionmodule 104 of the playback device 100 and the HDMI reception module 201of the display device 200.

The HDMI transmission module 104 has a TMDS encoder 151, amicro-computer 152, a communication module 153, etc. The HDMI receptionmodule 201 has a TMDS decoder 251, a micro-computer 252, an EDID 253,etc.

Decoded video data from the decoding module 103 are inputted to the TMDSencoder 151. The TMDS encoder 151 converts the input video data intovideo data of a format which will be described later with reference toFIGS. 5A to 5C and FIG. 6, and outputs pixel clocks generated by theconversion to CH0-CH2 respectively. Then, differential amplifiers notshown convert the pixel clocks outputted from the TMDS encoder 151 intodifferential signals, and output the differential signals totransmission lines of CH0-CH2. The differential amplifiers are providedso as to correspond to the transmission lines of CH0-CH2 respectively.The differential signals are transmitted to the HDMI reception module201 through the transmission lines of CH0-CH2.

The differential amplifiers (not shown) corresponding to CH0-CH2respectively are provided in the HDMI reception module 201. Uponreception of the differential signals from CH0-CH2, the differentialamplifiers convert the differential signals into data, and output thedata to the TMDS decoder 251. The TMDS decoder 251 decodes these datainto video data of 8 bits in each of RGB, and outputs the video data tothe display processor 202.

The micro-computer 152 of the source device is connected to themicro-computer 252 of the sink device by a CEC line and an HPD line. Themicro-computer 152 and the micro-computer 252 transmit information formutual control of the devices through the CEC line. And, themicro-computer 152 informs the source device of signal transmissionready completion corresponding to power-on completion of the sink devicethrough the HPD line.

The communication module 153 of the micro-computer 152 is connected tothe EDID 253 of the sink device through a DDC line. The communicationmodule 153 reads EDID data from the EDID 253.

(YCrCb) 4:2:0 format will be described below with reference to FIG. 4A.

For example, when the source video decoded in the playback device 100 isRGB 4:4:4, a large amount of data is required to transmit the video.Therefore, (YCrCb) 4:2:0 sampling is considered so that the amount ofdata is halved.

FIG. 4A illustrates the case where encoded signal of 4K2K video isconverted into (YCrCb) 4:2:0 format signal by the decoding module 103.Here, luminance information Y00 shows luminance of pixel P1. First colordifference information Cb00 shows color differences Cb concerned withfour pixels, that is, pixel P1, pixel P2 adjacent to the pixel P1, andpixels P5 and P6 downward adjacent to the pixels P1 and P2. The firstcolor difference information Cb00 may show the color difference Cb onlyfor the pixel P1. Second color difference information Cr10 shows colordifferences Cr concerned with four pixels, that is, pixel P5, pixel P6adjacent to the pixel P5, and pixels P1 and P2 upward adjacent to thepixels P5 and P6. The second color difference information Cr10 may showthe color difference Cr only for the pixel P5. Luminance information Y01shows luminance of pixel P2. Luminance information Y10 shows luminanceof pixel P5. Luminance information Y11 shows luminance of pixel P6.

Similarly, luminance information Y02 shows luminance of pixel P3. Firstcolor difference information Cb02 shows color differences Cb concernedwith four pixels, that is, pixel P3, pixel P4 adjacent to the pixel P3,and pixels P7 and P8 downward adjacent to the pixels P3 and P4. Thefirst color difference information Cb02 may show the color difference Cbonly for the pixel P3. Second color difference information Cr12 showscolor differences Cr concerned with four pixels, that is, pixel P7,pixel P8 adjacent to the pixel P7, and pixels P3 and P4 upward adjacentto the pixels P7 and P8. The second color difference information Cr12may show the color difference Cr only for the pixel P7. Luminanceinformation Y03 shows luminance of pixel P4. Luminance information Y12shows luminance of pixel P7. Luminance information Y13 shows luminanceof pixel P8.

On this occasion, for example, as shown in FIG. 4B, when data of theformat shown in FIG. 4A are to be pixel-encoded so as to be transmittedline by line and displayed on the display device at a speed of 60 framesper second, capability of 4400 pixels (=image horizontal direction 3840pixels+HB (Horizontal Blank) 560 pixels)×2250 lines (=vertical 2160lines+VB (Vertical Blank) 90 lines)×60Hz=594 megapixels per second isrequired (see FIG. 5A). That is, the pixel clock in this case is 594MHz. Thus, the pixel encoding shown in FIG. 4B will cause failure ofvideo transmission because the maximum transmission rate in a generalHDMI is 340 MHz.

Therefore, as shown in FIG. 4C, when the TMDS encoder 151 performspixel-encoding so that luminance components Y of data of the formatshown in FIG. 4A are transmitted by every 2 lines and color differencecomponents CbCr are transmitted collectively in one channel, sourcevideo data of 2160 lines can be transmitted through 1080 lines. That is,in the method shown in FIG. 4C, the pixel clock for transmission ofvideo to be displayed at 60 Hz can be reduced to 297 MHz which is a halfof the pixel clock shown in FIG. 4B.

FIGS. 5A to 5C illustrate examples of the video timing format of 4K2Kvideo by YCrCb 4:2:0 sampling. The timing format of FIG. 5A correspondsto the case where the pixel encoding method shown in FIG. 4B is used. Inthis case, as described above with reference to FIG. 4A, when thedisplay frame rate is 60 Hz, the pixel clock is 594 MHz (4400pixels×2250 lines×60 Hz).

FIGS. 5B and 5C illustrate examples of the timing format in the casewhere the pixel encoding method shown in FIG. 4C is used. In FIG. 5B, 90lines are transmitted as VB and one frame is transmitted by thefollowing 1080 lines. The next frame is transmitted by 1080 linesfollowing transmission of the frame. In this method, data aretransmitted at 30 Hz by every 2250 lines. Thus, the pixel clock in thismethod is 297 MHz (4400 pixels×2250 lines×30 Hz).

In FIG. 5C, 45 lines are transmitted as VB and one frame is transmittedby the following 1080 lines. Data are transmitted at 60 Hz by every 1125(=1080+45) lines. Thus, the pixel clock in this method is 297 MHz (4400pixels×1125 lines×60 Hz).

That is, in the formats of FIGS. 5B and 5C, the frame rate and the pixelclock can be halved as compared with the format of FIG. 5A.

The timing formats of FIGS. 5B and 5C may be applied for transmission of3D video. For example, the playback device 100 may transmit the 3D videosuch that the right-eye frame is transmitted at the position of “frame1” in FIGS. 5B and 5C and the left-eye frame is transmitted at theposition of “frame 2” in FIGS. 5B and 5C.

For example, in the case of FIG. 5B, one of the right-eye frame and theleft-eye frame may be assigned to 1-1080 lines after the VB, and theother may be assigned to 1081-2160 lines after the VB.

FIG. 6 illustrates the data configuration of EDID data stored in theEDID 253 by the display device 200. For example, some information VIC(Video Identification Code) 1 to VIC 6 of YCbCr (4:2:0) formats, such asthe video timing formats of FIGS. 5B and 5C are stored in P10 of theEDID data, as a format that can be used by the display device 200.Although “YCbCr (4:2:0) indicator” is stored in P10 in FIG. 6, theindicator indicates a usable video format. For example, the indicatorindicates the fact that YCrCb (4:2:0) can be used as a transmissionformat, the fact that the method shown in FIG. 4C can be used as a pixelencoding method, etc.

FIG. 7 illustrates the data structure of InfoFrame contained in a videosignal transmitted to the display device 200 by the playback device 100.For example, the InfoFrame is superposed on a blank region in FIGS. 5Ato 5C. Information indicating the format of video to be transmitted iscontained in P20 of the InfoFrame. Although “YCbCr (4:2:0) indicator” isstored in P20 in FIG. 7, the indicator indicates the format of video tobe transmitted. That is, for example, the indicator indicates the factthat YCrCb (4:2:0) is used as a transmission format, the fact that themethod shown in FIG. 4C is used as a pixel encoding method, etc. VICcontained in P21 corresponds to one of VIC 1 to VIC 6 in FIG. 6.

An example of a video transmission processing in the playback device 100will be described below with reference to FIG. 8. The playback device100 reads EDID 253 of the display device 200 by using the communicationmodule 153, when a video to be transmitted to the display device 200 hasa specific resolution (e.g. 4K2K) (S801). The micro-computer 152analyzes the indicator (P10 in FIG. 6) contained in the read EDID todetermine whether the display device 200 supports the video format usedfor the resolution of video to be transmitted by the playback device 100and for video transmission or not (S802). When the display device 200supports the video format (Yes in S802), the micro-computer 152 makescontrol to output a video signal containing InfoFrame indicating theformat and resolution of video to the display device 200 (S803). Whenthe display device 200 does not support video to be transmitted (No inS802), the playback device 100 does not perform video transmission.

FIG. 9 illustrates a video reception processing in the display device200. First, the micro-computer 252 receives InfoFrame contained in avideo signal transmitted (S901). When the transmission method indicatedby the InfoFrame is the method shown in FIG. 4C (S902), the TMDS decoder251 receives the video signal of the format of FIG. 4C with 2160 lines'video superposed on 1080 lines (S903). Then, the TMDS decoder 251outputs two lines' video per one line's input video to the displayprocessor 202. On the other hand, when determination in 5902 results inthat the transmission method indicated by the InfoFrame is a generalmethod (No in S902), the display device 200 converts the input videosignal by the general method and outputs the resulting video signal tothe display processor 202 (S905).

Although transmission of 4K2K video is exemplified in the embodiment,video of general HD image quality (1920×1080) may be transmitted bymeans of YCrCb 4:2:0 sampling like this embodiment.

Although the embodiment has been described above, the embodiment is justan example and should not limit the scope of the invention. The novelembodiment may be practiced in other various forms, and part of it maybe omitted, replaced by other elements, or changed in various mannerswithout departing from the spirit and scope of the invention. Forexample, although HDMI Specification has been exemplified in theembodiment, the embodiment may be applied to other communication methodsthan the HDMI Specification. These modifications will also fall withinthe scope of Claims and its equivalents

1-9. (canceled)
 10. A transmitter configured to transmit a video to anexternal device through a first, second, and third transmission channel,the transmitter comprising: a reading module configured to read firstvideo data of a given format; a conversion module configured to convertthe first video data of the given format into second video data of aYCrCb 4:2:0 format, the YCrCb 4:2:0 having four luminance values and twocolor difference values for every four pixels; a TMDS transmissionmodule configured to assign color difference values of the second videodata only with the first transmission channel, and assign luminancevalues of the second video data only with the second and thirdtransmission channels, thereby transmitting one of the color differencevalues and two of the luminance values at every TMDS clock.
 11. Atransmission method for transmitting a video from a transmitter to anexternal device through a first, second, and third transmission channel,the method comprising: reading first video data of a given format;converting the first video data of the given format into second videodata of a YCrCb 4:2:0 format, the YCrCb 4:2:0 having four luminancevalues and two color difference values for every four pixels; assigningcolor difference values of the second video data only with the firsttransmission channel, and assigning luminance values of the second videodata only with the second and third transmission channels, therebytransmitting one of the color difference values and two of the luminancevalues at every TMDS clock.
 12. A communication system comprising: firstto third transmission channels; a transmitter comprising: a readingmodule configured to read first video data of a given format; aconversion module configured to convert the first video data of thegiven format into second video data of a YCrCb 4:2:0 format, the YCrCb4:2:0 having four luminance values and two color difference values forevery four pixels; a TMDS transmission module configured to assign colordifference values of the second video data only with the firsttransmission channel, and assign luminance values of the second videodata only with the second and third transmission channels, therebytransmitting one of the color difference values and two of the luminancevalues at every TMDS clock; and a receiver comprising: a TMDS receivingmodule configured to receive the color difference values of the secondvideo data from the first transmission channel, and receive theluminance values of the second video data from the second and thirdtransmission channels, thereby receiving video data which is doubled inpixel information with respect to the second video data; and a displaymodule configured to perform displaying based on the video data receivedby the TMDS receiving module.